What are circular currents induced in a conductor placed in a changing magnetic flux called?

The correct answer is Eddy currents. Eddy currents are loops of electric current that are induced within conductors when they are exposed to a changing magnetic field. According to Faraday's law of electromagnetic induction, a changing magnetic flux through a conductor creates an electromotive force (EMF) in the conductor, which leads to the generation of these circular currents.

Eddy currents flow in closed loops within the conductor, usually perpendicular to the direction of the magnetic field, and their direction is determined by Lenz's law, which states that the induced current will flow in such a way as to oppose the change in flux. These currents can lead to energy losses in the form of heat due to the resistance of the material through which they flow.

Induced currents is a broader term that encompasses any current that is generated in a conductor due to a changing magnetic field but does not specifically refer to the circular nature of the currents. AC currents and DC currents refer to the specific forms of alternating and direct current, respectively, rather than describing the phenomenon of currents induced by changing magnetic fields. Hence, the identification of circular currents specifically as eddy currents highlights their unique properties associated with changing magnetic environments.